The mobility of an unmanned vehicle is extremely dependent upon the terrain, obstacles in the path of the vehicle causing various mobility failures such as overturning, gross slippage, nose-in failure and hang-up failure, the latter two being caused by engagement of the nose and belly respectively of the vehicle with the terrain.
Wide track manned vehicles having tracks extending substantially the full width of the vehicle are known for use on relatively even terrain. The tracks of such vehicles fully cover the belly and hence would be suitable for eliminating the possibility of hang-up failure were it not for the steerage problems engendered in use on uneven terrain by the mode of steering that has to be employed, ie skid steering.
Skid steering comprises the application of a velocity differential to the two independently drivable, parallel tracks of the vehicle, which application causes the tracks to skid about a pivot axis trajectory, the location of which is determined both by the velocity differential applied and by the load distribution of the vehicle upon the tracks. When the tracks are wide and the terrain is uneven it becomes difficult to predict where ground contact will take place, with consequent unpredictability of loads and rates of turn during steering.
The present invention seeks to provide a wide track vehicle with improved skid steering on uneven terrain.